This invention is directed to an antifouling fuel composition and to a method for using same. More specifically, the present invention is directed at a fuel composition having particular applicability in minimizing and/or preventing injector fouling in gasoline engines equipped with electronically controlled multiport fuel injectors.
Over the past several years, improvements have been made in the performance of internal combustion engines. One of the most significant improvements which has been made has been the widespread use of fuel injection to improve the performance and fuel economy of internal combustion engines. While carburetor-equipped internal combustion engines admix the air and fuel for distribution through a manifold to all of the cylinders, in a fuel injected engine the fuel is injected into the manifold close to the intake valve of each cylinder for combustion. Fuel injection systems are of two basic types, mechanically controlled and electronically controlled. The early fuel injected engines were controlled mechanically, i.e., the operation of each injector was controlled by pressure. Recently, however, the use of electronically controlled fuel injection engines has become increasingly widespread. In an electronically controlled fuel injection system sensors disposed in the exhaust are employed to maintain the air to fuel ratio within narrow limits. Electronically controlled fuel injection systems offer the same performance and fuel economy benefits that would be achieved with mechanically controlled fuel injection systems and also serve to more closely regulate fuel-air mixtures to thereby enable the catalytic converter to oxidize carbon monoxide and hydrocarbons to carbon dioxide and simultaneously to reduce nitrogen oxides and thus meet emissions control legislation. Such legislation imposing as it did strict control of exhaust pollutants utimately led to the development and widespread application of new technologies such as electronic fuel injection.
It has been found that the electronically controlled fuel injector systems have small port openings which are prone to fouling by deposits. These deposits are believed to occur, at least in part, by gasoline and oil vapor, which is present in close proximity to the injector tip, becoming baked onto the hot surfaces of the injector pintle and on the surfaces of the annulus surrounding the pintle when the engine is shut off. These deposits restrict the fuel flow to that particular cylinder. This, in turn, causes a sensor disposed in the exhaust to detect a higher than desired oxygen to fuel ratio. The sensor will attempt to correct this condition by increasing the amount of fuel injected into all of the cylinders. This, in turn, will result in a richer than desired fuel to air ratio in the exhaust. The sensor then will attempt to correct this by decreasing the amount of fuel injected into each cylinder. This cyclical adjustment of the fuel to air ratio ranging between too lean a mixture and too rich a mixture can at times result in poor operating performance of the vehicle. In addition, close tolerances in this new type of injector and concurrently higher underhood temperature also tend to enhance deposit formation resulting in poor vehicle driveability and exceeding exhaust pollutant levels set by emissions control legislation.
It has been found that conventional gasoline detergents, which have proven effective in preventing and/or eliminating carburetor deposits are not particularly effective in removing and/or preventing deposit build-up that may occur in electronically controlled fuel injection systems. For example, SAE Technical Paper Series 861533 entitled, The Effects of Fuel Composition and Additives on Multiport Fuel Injector Deposits (1986) discloses that very serious driveability problems have developed with vehicles equipped with multiport fuel injection systems. These problems are caused by deposits that formed in the metering orifice at the tip of the injector and restricted fuel flow. The study showed that all major gasoline brands were involved, including those gasolines which were thought to have good detergent additives. Several additives, representing specific examples of different additive chemistries, were tested in the base fuel. Some additives did alleviate injector fouling, others were not particularly effective, or did not work at all. Alkyl succinimide and polybutene succinimide appeared to be effective, polyether amine was ineffective in that failure occurred after about 4,000 miles of test run, whereas phenylene diamine was even less effective.
Presently available methods for removing deposits from fuel injector orifices typically comprise either mechanically cleaning the injectors or the addition to the fuel of relatively large quantities of particular additives. Mechanical cleaning, which may involve either the complete removal of the injector for manual deposit removal or the use of polar solvents for flushing the deposits free, is not desired because of the relatively high cost and inconvenience.
To be useful commercially a gasoline additive for reducing and/or preventing port fuel injector fouling must be effective at low concentration, must not significantly affect the combustion characteristics of the fuel and must not foul the catalytic converter catalyst.
Additives have been added to gasoline to improve certain properties of the fuel. U.S. Pat. No. 3,115,400 discloses the use of compounds of the structure ##STR1## where R is a C.sub.6 -C.sub.22 aliphatic hydrocarbon radical, X is an integer from 2 to 4, Y is an integer of at least 1, and Z is an integer of at least 1, for use in motor fuel to prevent or reduce carburetor icing.
U.S. Pat. No. 4,409,000 discloses combination of hydroxy amines and hydrocarbon-soluble carboxylic dispersants as engine and carburetor detergents for normally liquid fuels. Among the hydroxy amines disclosed are compounds of the formula ##STR2## where R' may be an alkyl radical containing from about 8 to about 30 carbon atoms, where R.sup.2, R.sup.3, R.sup.4 and R.sup.5 each may be hydrogen and where a and b may be integers from 1 to 75.
U.S. Pat. No. 4,231,883 discloses the use of a compound of the formula ##STR3## where R.sub.1 is a C.sub.12 -C.sub.36 aliphatic hydrocarbon group, R.sub.2 and R.sub.3 are divalent hydrocarbon radicals containing 2-4 carbon atoms and X and Y are integers from 1-4, for friction reduction in lube oils. Preferred compounds comprise N,N-bis (2-hydroxyethyl) hydrocarbylamines.
U.S. Pat. No. 3,387,953 is directed at the use of organo-substituted nitrogen oxides, particularly amine oxides for rust inhibition and as anti-icing agents in gasoline. Several representative formulas for amine oxides are given including the following: ##STR4## where: R.sub.1 is C.sub.6 -C.sub.24 alkyl, aryl, cycloaliphatic, heterocyclic, substituted alkyl or substituted aryl; and R.sub.2 and R.sub.3 are the same or different and are C.sub.1 -C.sub.24 alkyl, aryl, substituted alkyl or aryl, cycloaliphatic or heterocylic. R.sub.2 and R.sub.3 preferably comprise hydroxy substituted alkyls. These compounds typically are added to gasoline in a concentration within the range of about 2.0 to about 100 pounds of amine oxide per 1,000 barrels of gasoline (ptb). Among the most preferred additives is bis(2-hydroxy ethyl) cocoamine oxide.
U.S. Pat. No. 3,594,139 is directed at a rust-inhibitor concentrate that can be blended with gasoline year-round. This patent also discloses the use of amine oxides having the aforementioned formula for use as gasoline additives for rust prevention. This patent also discloses a particularly preferred concentrate comprising bis(2-hydroxy ethyl) cocoamine oxide.
The amine oxides described above have been typically used to inhibit rust and carburetor icing, although these amines also were known as carburetor detergents.
It has been discovered that use of hydroxy substituted amine oxides can result in additive losses because of high water solubility and adsorption on polar surfaces.
Accordingly, it would be desirable to provide an additive package for gasoline which will be effective in reducing and/or eliminating fouling without appreciable additive losses.
It also would be desirable to provide an additive package having a demulsifying agent which is effective in the presence of both neutral and basic waters.
Accordingly, it would be desirable to provide a gasoline additive package which is relatively inexpensive and effective at low concentrations to reduce and/or eliminate injector fouling.
It also would be desirable to provide a gasoline additive package which is non-corrosive, non-deleterious to the catalyst, and does not affect the combustion characteristics of the fuel.
It also would be desirable to provide a gasoline additive package which could be easily added to the finished gasoline at any point during the storage and/or distribution system.